Swage baseplates are commonly used in disk drive or other dynamic data storage systems to attach head suspensions to actuator arms. Briefly, baseplates include a generally flat flange and a tubular boss tower extending from the flange. The boss tower is hollow and has an inner diameter defining a swaging opening and an outer diameter sized to fit within an opening in the actuator arm to which the suspension is to be mounted. Multiple actuator arms may be integrated into a single, stacked unit known as an e-block.
During the swaging process, a portion of the flange is clamped down and the flange is welded to a mounting region of the suspension. An actuator arm having an opening is positioned over the boss tower so that the actuator opening and the boss tower are concentrically aligned. A ball is forced through the swaging opening in the boss tower, bending the boss tower outwardly, thereby forcing the outer surface of the boss tower into frictional engagement with an inner surface of the opening in the actuator arm. The baseplate and attached suspension are thereby securely fastened to the actuator arm.
The boss towers of two baseplates, each attached to a suspension, can be inserted into an actuator opening, one boss tower entering the actuator opening from each end of the opening. A swage ball is passed through the boss towers to force the outer surfaces of both boss towers into tight engagement with the inner surface of the actuator opening. Thus, an actuator arm may carry two suspensions on opposite sides, one up and one down.
The baseplate boss towers thus extend in opposite directions with respect to the direction of passage of the ball through the swaging openings. For one baseplate, the ball is passed in a direction that tends to place the boss tower in compressive stress, while, for the other baseplate, the direction of passage of the ball is such as to tend to place the boss tower in tensile stress.
Unfortunately, the swaging process can result in deformation of the flange, which deforms the suspension to which the baseplate is mounted. Typically, the baseplate flange is manufactured to a flatness specification, which assumes zero flatness (totally flat) to be the optimal condition. Nonetheless, deformation does occur, and can cause changes in the desired positional orientation of the suspension, known as z-height variations, which affect spring characteristics of the suspension, creating gram load changes. These swaging-induced z-height variations and gram load changes can detrimentally affect the operational performance of the suspension.
Differences in boss tower designs and stresses between suspensions swaged in tension and compression on the same actuator can cause differences in gram load change between these up and down facing parts.
Sometimes during manufacturing the flange bows or deforms towards the boss tower (“positive” deformation) and sometimes the flange bows away from the boss tower (“negative” deformation). However, positive and negative deformation affect gram load differently. Thus, some baseplates have been manufactured with a slight curvature that is uniform about that boss tower to reduce variation. This curvature, while not reducing flange deformation, biases flange deformation in a selected direction (usually positive). Generally, the flange is curved such that an outermost tip of the flange is displaced by a maximum of approximately 0.0005″.
A need exists for a swaging assembly that counteracts the deformation forces on attached components following swaging.